The present invention is directed to liquid crystal cells used in liquid crystal display screens for liquid crystal display devices which cell contains a liquid crystal layer disposed between two carrier plates which plates are spaced apart by a frame and which plates are of insulating material with at least one plate being transparent and the surfaces engaging the layer being provided with electrode patterns.
Liquid crystal cells used in display screens are known in a variety of different embodiments. An example of an embodiment is disclosed in the German printed patent application (Offenlegungsschrift) No. 2,028,089. Known display screens have been used for analog and digital date displays and for one color or multiple color displays. The display screen using a liquid crystal cell exhibits a property of being a thin display device which may include storage of the information being displayed.
To obtain both the quality of reproduction and a long life duration in liquid crystal display screens of the above-mentioned type, it is most important that the liquid crystal layer is hermetically sealed from the exterior of the cell to prevent any penetration of atmospheric influences and moisture. It is also important that the sealing agent used in forming the hermetic seal does not contain organic substances or other reaction sensitive substances which will react with the liquid crystal.
Since it is necessary to avoid any considerable heating during a melting process which excessive heating could lead to destruction of the thin layer of electrodes on the surface of the plates forming the cell, glass solder, which has a suitable softening point, has proved most effective for edge sealing the two plates forming the chamber containing the liquid crystal layer. However, an access opening or passage to the chamber for the purpose of filling and venting the chamber after formation of the cell is still necessary. The above-mentioned problems also occur while closing the access passage. For example, direct closure with a synthetic resin adhesive has been found unsatisfactory due to reaction of some of the materials of the resin adhesive with the liquid crystal material of the layer.